Gearing and lubricating means therefor



7 June 3, 1969 J. E. HODGES ET AL 3,447,472 GEARING AND LUBRICATING MEANS THEREFOR Filed June 12, 1967 I Sheet of 4 IN VENTOR 33 04 E. Hours B PHI IP &. Yum:

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' ATTORNEY;

June 3, 1969 J, 5. Houses ETAL 3,447,472

GEARING AND LUBRICATING MEANS THEREFOR Filed June 12, 1967 Sheet 2 of! INVENTOR S 31H" E. H096? BY PHILIP a. TIYMG'K 6RAHM1 J". T0 6 M, Jan- 'ATTORNEYJ June 3, 1969 J. E. HQDGES ET AL 3,447,472 (mama AND LUBRICATING MEANS THEREFOR Filed June 12, 1967 Sheet 3 0:4

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Am; L700 600 United States Patent 3,447,472 GEARING AND LUBRICATING MEANS THEREFOR John E. Hodges, Pnrton, near Swindon, Philip G. Joyner, Brockworth, and Graham J. Toogood, Bishops Cleave, England, assignors to Dowty Hydraulic Units Limited, Cheltenham, England, a company of Great Britain Filed June 12, 1967, Ser. No. 645,202 Claims priority, application Great Britain, June 20, 1966, 27,494/ 66 Int. Cl. F04c 1/04, 29/02 US. Cl. 103-126 Claims ABSTRACT OF THE DISCLOSURE Field of the invention This invention relates to therefor.

gearing and lubricating means Summary of the invention According to this invention there is provided gearing including at least two meshing rotors of toothed or lobed form whose shafts are mounted in bushes there requiring lubrication, wherein grooving is formed in the bore of each bush which is in communication with a side face of its respective rotor in a zone located at a position Where, as the rotor teeth or lobes successively pass it, the spaces between the meshing teeth or lobes are increasing in volume, the consequent suction created by the increase in volume inducing liquid to flow through the grooving in the bushes, thus to lubricate the shafts as they run in the bushes.

Each bush may additionally inlc'lude passage means provided through it and which may place the grooving in communication with the said zone.

Where the meshing rotors are the pumping elements of a pump, the grooving may be in open communication with the low pressure port of the pump and the passage means place the grooving in communication with said zone, so that liquid for lubrication is induced to flow from the low pressure port through the grooving to the spaces which are increasing in volume, this liquid thereafter being discharged into the low pressure port as the respective teeth or lobes move out of mesh.

Where only two rotors are in mesh, each supported in a pair of bushes, the passage means provided, one through each of the four bushes, each terminates at the respective side face of the bush adjacent its rotor in a port cooperable with the adjacent side faces of the teeth or lobes of the respective rotor, the ports of the two bushes on one side of the rotors being connected by a groove cut in the side faces of both bushes, and the ports in the two busihes on the other side of the rotors being connected by another and similar groove cut in the side faces of both of these bushes.

The said grooves may be cranked in shape to Icooperate in predetermined manner with the side [faces of the teeth or lobes as they pass across them.

A relief recess may be provided in each shaft immediately adjacent the respective rotor side face.

Where the rotors are so arranged in a gearbox that a head of liquid is'available at one end portion of each of the bushes, the said suction induces liquid to flow through the grooving in the bore of each bush and this lubricating liquid is thereafter discharged into the liquid in the gearbox as the respective gear teeth move out of mesh.

In the case of pumps, the bushes, or certain of the bushes, may be pressure-balanced in known manner, thereby, to reduce bush wear.

Brief description of the drawings Of the seven accompanying drawings,

FIGURE 1 is a cross-section of a gear pump in accordance with the first embodiment of the invention,

FIGURE 2 is a perspective view of the gears of the pump shown in FtIGURE 1 and the bushes supporting those gears on one side thereof,

FIGURE 3 is a perspective view of the gears and bushes shown in FIGURE 2, taken in the direction of the arrow III on FIGURE 2 and dotted detail,

FIGURE 4 is a full line, partly-cut-away perspective view, of one of the gears of FIGURES 2 and 3,

FIGURE 5 shows at (a), (b), (c), (d), and (e) five meshing conditions of the gears of the pump of the first embodiment,

FIGURE 6 is a view, similar to that of FLIGURE 3, showing a part of a gear pump in accordance with the second embodiment of the invention, and,

FIGURE 7 is a perspective view of a part of a gearbox in accordance with a third embodiment of the invention.

with the gears shown in Description of the preferred embodiment With reference to FIGURES 1 to 5 of the drawings, a gear pump 10 includes a casing 11 having a low pressure or inlet port 12 and a high pressure or outlet part 13, both of these ports being shown in dotted detail in FIGURE 3. The casing 11 houses two meshing pump rotors in the form of gears 14 and 15, the shafts 16, 17; 18, 19 of which are mounted for rotation in respective pairs of bushes 20, 21; 22, 23. The bushes are of D- shaped cross-section with the flats of adjacent bushes in abutment at 24 and 25 respectively.

The shaft 19 passes through an aperture 26 in a pump closure member 27 which is bolted to the casing 11. lExternally of the pump, the shaft 19 is connectible to a power source (not shown).

The portions of the bushes 20 the gears 14 and and 22 remote from 15 are provided with spigot-like projections 28 and 29 of predetermined shape, around each of Which a sealing ring 30, 31 is provided as shown in FIGURE 1. 'The shape of these projections is clearly shown in FIGURE 2, but in that figure the sealing rings are omitted.

The areas Oif the bushes 20 and 22 outside of the sealing rings 30 and 31 are subjected to high pressure from the outlet port 13 of the pump which gains access thereto through suitable passage means (not shown).

The end face areas of the projections confined within the sealing rings 30 and 31 are low pressure areas, the effective centers of pressure thereof being off-set from the rotational axes 32 and 33 as necessary to provide, in 'known manner, such pressure-balancing of the bushes 20 and 22 as to oppose the tendency of the bushes to tilt in operation, and thus to reduce bush wear.

The chambers in the casing 11 subjected to high pressure are shown in FIGURE 1 at 34 and 35, While the 3 chambers subjected to low pressure are shown at 36 and 37.

As well as providing for pressure-balancing of the bushes 20 and 22, the assembly of gears 14 and 15 and bushes 20, 21, 22, 23 is pressure-loaded by this arrangement to provide adequate sealing at the interfaces of the gears and bushes.

As shown in FIGURE 1 the gear shafts are provided each with undercuts, or relief recesses, 38, 39, 40 and 41 immedlately adjacent the side faces of the respective gear.

Chambers 42 and 43 are provided in the cover member 27 at the end portion of the bushes 21 and 23 remote from the gears 14 and 15. Like the chambers 36 and 37, the chambers 42 and 43 are subjected to low pressure.

In order to lubricate the shafts of the gears when running in the bushes, a low \pressure lubrication system is provided in the following manner, but although reference is hereinafter made to the bushes and 22, a similar lubrication system is provided for the bushes 21 and 23.

On the face 44 of each bush 20, 22 adjacent its gear there is provided a shallow radially-directed slot 45 with which the inlet port has direct communication. Each slot which opens into the respective under-cut, or relief recess 38, 40 formed in the gear shafts 16,18, immediately adjacent the respective gear. Part-way around the circumference of each bush, away from the radial slot 45 in the direction of rotation of the gear, (this direction being indicated by the arrows in FIGURE 3), there is provided an axially-directed groove 46 in the bush bore 49. Each groove 46 is positioned just beyond the region of high loading of the respective shaft 16, 18 in its bush 20, 22. Each groove 46 opens from the face 44, of the respective bush and runs for the full axial length of the bush opening into the respective chamber 36, 37 at the end portion of the bush remote from the gears 14 and 15 Each bush is provided with passage means in the form of a hole 48 drilled from a recess 49 cut in the end face of the respective projection 28, 29 extending from the face 50 of the respective bush remote from the gears 14 and 15. The recess opens from the respective bore 47 and the hole passes completely through the respective bush terminating in a port 52 on the face 44 of the bush adjacent the gears. Each hole 48 is parallel with its respective bore 47, and the recess 49 and hole 48 provide means whereby the respective chamber 36, 37 is placed in communication with a zone on the face 44 adjacent the inlet port 12.

As shown in FIGURES 2 and 3, a cranked groove 53, a part 53a of which is formed in the bush 20 and a part 53b of which is formed in the bush 22, interconnects the ports 52 at the faces 44.

The position of the cranked groove 53 is such, with respect to the low pressure port 12, that as the gear teeth successively approach and pass over the groove, successive negative pressures are created by tooth-space filling in a manner hereinafter described.

In operation of the pump, with rotation of the driving shaft 19, the two intermeshing gears 14 and 15 rotate, drawing oil through the inlet port 12 and discharging this under pressure through the outlet port 13, a suitable relief valve (not shown) being provided in association with the outlet port.

The positions of the two cranked grooves 53 of the pump and of the inlet and outlet ports 12 and 13 are such that as, upon rotation of the gears, the meshing teeth leave their condition of full mesh and commence to approach their out-of-mesh condition, the ports 52 and cranked grooves 53 in the bush side faces 44 are opened to those spaces between the teeth which momentarily are increasing in volume. Since upon increasing in volume the tooth spaces tend to cavitate, thus creating a suction, then as the teeth approach their out-of-mesh condition, oil is induced to flow into these spaces, thereby to fill them. This oil is derived from the inlet 12, the suction being suflicient in the case of each bush to draw oil through the respective radially-directed slot 45, then part-way around the relief recess 38, 39, 40, 41, along the axially-directed groove 46 into the respective chamber 36, 37, 42, 43, and finally along the respective drilled hole 48 and through the port 52 and interconnecting groove 53. In thus passing along the axially-directed groove 46, adequate lubrication of the respective shaft 16, 17, 18, '19 as it runs in its bush is afforded.

The oil thus induced into each respective tooth space is discharged into the inlet 12 as the pair of teeth defining this tooth space come fully out of mesh, the following teeth successively perforing a similar lubricating flowinducing function as individually they leave the full mesh condition and approach the out-of-mesh condition.

By virtue of the cranked groove 53 interconnecting the respective pairs of ports 52 in the sides face 44 of the bushes, the oil induced is relatively smoothly-flowing and the lubrication is substantially continuous through both bushes on both sides of the gears.

There is of course a predetermined backlash between the teeth of the driving gear 15 and those of the driven gear 14. It is so arranged that when two meshing teeth are in a position in which the intertooth space is at a minimum volume, this backlash is positioned in a plane which is common to the rotational axes of both gears.

With reference to FIGURES 5(a), (b), (c), (d) and (e), three teeth of the gear 14 are shown at 54, 55 and 56, while two teeth of the gear 15 are shown at 57 and 58.

In FIGURE 5(a) the intertooth space defined by the flank 54b of the tooth 54, the flank 55a of the tooth 55, and the flank 57b and tip 57c of the tooth 57, is shown at 59. Also in FIGURE 5(a) the intertooth space defined by the flank 57b of the tooth 57, the flank 55a and tip 55c of the tooth 55, and the flank 58a of the tooth 58, is shown at 60. In the condition shown in FIG- URE 5(a), the cranked groove 53 is cracked open at 61 to the inlet port 12, but as the gears 14 and 15 rotate further in the direction of the arrows to the position shown in FIGURE 5(b), the tooth 58 commences to lose contact with the tooth 55, while the tooth 57 comes more fully into mesh with the teeth 54 and 55. Hence, the intertooth space 60 is now open almost fully to the part 53b of the cranked groove 53 and the flank 57a of the tooth 57 rolls along the flank 54b of the tooth 54.

Thus, the volume of the intertooth space 60 is increasing in volume, and simultaneously, since the driving tooth 58 is uncovering the cranked groove 53 and is also uncovering the port 52 in the bush 22, the cavitational tendency due to the increase in volume of the inter-tooth space 60 is inducing the flow of lubricating oil through both bushes on both sides of the gears. Such lubricating oil flow continues until the tooth 55 comes out of mesh from the teeth 57 and 58, as shown in FIGURE 5(c). At this point the induced lubrication flow momentarily stops, but is started again as the trailing flank 55a of the unrneshing driven tooth 55 opens the part 53a of the cranked connecting groove 53 to the next intertooth space 59.

In FIGURE 5(d) the intertooth space 59 is shown almost at its point of maximum volume, having during expansion from the condition shown in FIGURE 5(c) induced lubricating oil to flow through all the bushes into this space with continued rotation of the gears, while in FIGURE 5 (e) the tooth 57 is shown moving out of mesh from the teeth 54 and 55, at which point the lubrication flow again momentarily stops.

It will be understood that the amount which the interconnecting cranked grooves 53 are uncovered for such negative pulse-induced lubrication depends upon the crank-angle of these grooves, the precise paths of the grooves between their respective ports, and the precise tooth form of the gears 14 and 15.

Even with each respective tooth space as at 59, 60 partly open to inlet 12 as the flanks of the teeth part on coming out of mesh, suction is maintained to continue the flow of oil to the bushes, but beyond a certain point of separation of the flanks the suction is lost, thereafter being recreated by the succeeding intertooth space.

Thus the shape and position of the ports and cranked interconnecting grooves cooperable with the faces of the gears on both sides thereof ensure the optimum intertooth space registry therewith to afford a substantially continuous induced flow of lubricating liquid through both bushes on both sides of the gears.

With reference now to the gear pump of the second embodiment of the invention, this is similar in construction to that of the first embodiment, but whereas the latter is provided with cranked grooves in the faces of the bushes adjacent the gears, as shown in FIGURE 6 the pump of this embodiment does not incorporate such cranked grooves in the faces 144 of the bushes 120 and 122 of the gears 114 and 115, but instead the ports in these faces are independent of one another, having no interconnecting means whatsoever.

The pump and its lubrication system in accordance with this second embodiment operates in a manner very similar to that of the pump of the first embodiment except that when the respective teeth come into and out of mesh and into registry with the ports 152, the fact that there is no interconnecting groove rneans that the induced flow of oil occurs independently by virtue of the unconnected relationship of each port 152 with the adjacent sides faces of the gears. Thus the induced flow of oil for lubrication is less smooth because flow will occur alternately through adjacent bushes.

However, in certain constructions such less smooth flow is not detrimental to the satisfactory operation of the pump.

Referring now to the third embodiment of the invention, a gearbox, part of the casing of which is shown at 210 in FIGURE 7, includes a pair of meshing gears 211 and 212 fast upon their respective shafts 213 and 214. The shafts are respectively mounted in bushes 215 and 216 housed in bores 217 and 2'18 in the casing 210.

The gears 211 and 212 form part of a gear train, the gears being immersed in oil contained within the casing The level of this oil in the casing provides a head available at the end portions of the bushes 215 and 216 remote from the gears. The bores of the bushes are provided with parallel grooves 219 and 220 for their full axial length, which communicate respectively through passageways 221 and 222 with a single common port 223 formed on the face of the casing 210 adjacent the gears 211 and 212 in a zone where, a suction is created when successive gear teeth commence to move towards their out-of-mesh condition and the intertooth spaces simultaneously increase in volume. A similar arrangement is provided for the bushes (not shown) to the left in the drawing of the gears 211 and 212.

Thus, upon rotation of the gears 211 and 212, the suction created in the intertooth spaces causes the oil available under the said head at the end portions of the bushes 215 and 216 remote from the gears, to pass through the grooving 219 and 220 and through the respective passageways 221 and 222 to the common port 223, so that adequate lubrication of the shafts 213 and 214 in the bushes 215 and 216 occurs. Simultaneously, lubrication of the other bushes (not shown) of the gears 211 and 212 occurs in similar manner.

However, since only one port 223 is provided in cooperable association with the gear teeth on each side of each pair of gears, although adequate, the flow of lubrieating oil is not so continuous as in the two previous embodiments.

By the invention, an adequate low pressure circulation of liquid for lubrication of the shaft bushes of gearing is obtained.

Since in the case of a pump it is not necessary to tap high pressure liquid for lubrication purposes from the delivery port, greater pump elficiency is achieved. Further, cool oil is to advantage used, as opposed to hot oil in the case of tapping from the pump delivery port.

Also, since optimum tooth space filling is deliberately achieved, good overall pump efliciency is obtained because cavitation in the intertooth spaces is prevented.

The invention is in no Way limited to rotors of toothed form, as in other embodiments the rotors may be of intermeshing lobed form.

Further, the invention is in no way limited to axiallydirected grooving in the bush bores, as in other embodiments other forms of grooving, for example helical grooving, may with advantage be provided.

Again, the invention is not limited to the provision of relief recesses in the shafts adjacent the rotor side faces, as in other embodiments a counterbore of adequate dimension is provided in each of the bushes adjacent the rotor side faces, for the same purpose.

Although in the first two embodiments the bushes are of abutting D-shape, in alternative embodiments they may not be D-shaped nor abut, or again the bushes on at least one side of the gears may be arranged in a common end plate.

Again, although in the first two embodiments, the lubricating oil is drawn firstly through the axially-directed grooving and then through the drilled hole in the respective bush, in other embodiments it may be arranged so that lubricating oil is firstly drawn through the drilled hole and then through the axially-directed grooving, suitable connection being made between the end portion of the grooving adjacent the gears and the zone with which the intertooth spaces register when increasing in volume.

Further, the invention is in no way limited in its application to two meshing gears, or to gears having shafts extending from both sides thereof, as in other embodiments any number of meshing gears may be provided and any gear may have its shaft extending from one side only. In the latter case, however, suitable blanking of the otherwise open end portions of the intertooth spaces would be necessary.

Whilst in the third embodiment above-described the head of oil available at the end portions of the bushes remote from the gears has been due to the level of oil in which the gears are immersed, in other embodiments the gears may not be so immersed and in this case the required head at the said end portions of the bushes is produced by other suitable means.

We claim:

1. Gearing, including at least two meshing rotors of toothed form whose shafts are mounted in bushes there requiring lubrication, wherein grooving (46) is formed in the bore (47) of each bush (20, 21, 22, 23) which is in communication with a side face of its respective rotor (14, 15) in a zone located at a position Where, as during rotor rotation the' rotor teeth (545 8) successively pass it, the spaces (59, 60) between the meshing teeth are increasing in volume, the consequent suction created by the increase in volume inducing liquid derived from the low pressure side of the gearing to flow through the grooving in the bushes and into said spaces of increasing volume, said liquid, in flowing through the grooving, thus lubricating the shafts (16, 17, 18, 19) as they run in the bushes.

2. Gearing as claimed in claim 1, wherein each bush (20, 21, 22, 23) additionally includes passage means (48) provided through it and which places the grooving (46) in communication with said zone.

3. Gearing as claimed in claim 1, wherein said meshing rotors (14, 15) are the pumping elements of a pump (10), and wherein the grooving (46) is in open communication with the low pressure port (12) of the pump, said passage means (48) placing the grooving in communication with said zone, so that liquid for lubrication is induced to flow from the low pressure port through the grooving to the spaces (59,60) which are increasing in volume, said liquid thereafter being discharged into the low pressure port as the respective teeth (5458) move out of mesh.

4. Gearing as claimed in claim 3, and where only two rotors are in mesh, each supported in a pair of bushes, wherein said passage means (48) are provided through each of the four bushes (20, 21, 22, 23), each said passage means terminating at the respective side faceof the bush adjacent its rotor in a port (52) cooperable with the adjacent side faces of the teeth (54-58) of the respective rotor.

5. Gearing as claimed in claim 4, wherein the said ports (52) of the two bushes (20, 22) on one side of the rotors (14, 15) are connected by a groove (53) cut in the side faces of both bushes, and the said port (52) in the two bushes (21, 23) on the other side of the rotors are connected by another and similar groove cut in the side faces of both of these bushes.

6. Gearing as claimed in claim 5, wherein the said grooves (53) are cranked in shape to cooperate in predetermined manner with the side faces of the teeth (54-58) as they pass across them. I

7. Gearing as claimed in claim 1, wherein a relief recess (38, 39, 40, 41) is provided in each shaft (16, 17, 18, 19) immediately adjacent the' respective rotor side face.

8. Gearing as claimed in claim 1, and so arranged in a gearbox (210) that ahead of liquid is available at one end portion of each of said bushes (215, 216) the said 8 suction inducing liquid to flow through the grooving (219, 220) in the bore of each bush and this lubricating liquid being thereafter discharged into the liquid in the gearbox as the respective gear teeth move out of mesh.

9. Gearing as claimed in claim 8, wherein the said grooving (219, 220) in the bore of each bush (215, 216) is placed in communication with said zone by way of passageways (221, 222) provided in said casing.

10. Gearing as claimed in claim 9, wherein on at least one sideof each pair of intermeshing gears (211, 212), respective casing passageways (221, 222) lead from those end portions of the respective bushes (215, 216) adjacent the gears to a common port (223) in the face of the casing adjacent the gears, said port being cooperable with the respective side faces of the meshing gears in the said zone.

References Cited UNITED STATES PATENTS 1,372,576 3/1921 Tullmann 103--126 2,276,107 3/1942 Simons 103l26 2,500,719 3/1950 Ungar 103-126 2,775,209 12/ 1956 Albright l03126 2,986,096 5/1961 Booth et a1 103126 3,368,799 2/ 1968 Sluijters 103-126 U.S. CL. X.R. 230-207 Patent No. 3,447,472 Dated June 3, 1969 Inventoflgl E. Hodges, P. G. Joyner, G. J. Toogood It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Claim 1, line 2, should read toothed or lobed form whose shafts are mounted in bushes there-; line 7 should read rotor rotation the rotor teeth (54-58) or lobes successively pass it,-.

Claim 3 line 10, should read low pressure port as the respective teeth (54-58) or lobes move.

Claim 4 line 7, should read the adjacent side faces of the teeth (54-58) or lobes of the respec- Claim 5 line 4 "port" should be ports- Claim 6, line 4 should read or lobes as they pass across them.

SIGNED AND SEALED JUN9 1970 mam Attest:

E WILLIAM E. sum, JR. dward M. Fletcher, If. Commissioner of Patents Attcsting Officer 

